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Brewer Workshop Beijing May 15 In a ideal brewer the ozone do not depend of the attenuation filter. 1.Attenuation Filters are “neutral” 2.Nominal wavelengths and weights verify : If the attenuation is linear with wavelength, do not affect the ozone calculation. AEMET, Agencia Estatal de Meteorología 5 Brewer Workshop Beijing May 15

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Attenuation Filter : Ozone Algorithm Ozone SAG Helsinki -2009

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Brewer Workshop Beijing May 15 Attenuation Filters : In a real instrument a)the filters can not be neutral b)Even if there are linear with wavelengths If the slope is to big you see the effect in the ozone. AEMET, Agencia Estatal de Meteorología 7

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Brewer Workshop Beijing May 15 The effect can be accounted using a ETC correction for the affected filter. If you know the attenuation of every wavelengths The correction in can be implemented as the ussual Standard Lamp correction. AEMET, Agencia Estatal de Meteorología 10

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Brewer Workshop Beijing May 15 Internal Test This procedure check on the data record if one particular brewer is affected by this issue and estimate the correction. We look in to the ozone differences in simultaneous measurement performed with different filter Requires a long record (one year) of ozone measurement without changes on the instrument calibration With for example Martin Stanek’s O3Brewer produce a report with include : Date, time,filter, airmass, ozone, MS9 Select simultaneous measurements (10 min, airmass <0.05), performed with different filter. Look for significant differences on the statistics from f#3 to f#4, ( you have only significance for high air mass) AEMET, Agencia Estatal de Meteorología 12

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Brewer Workshop Beijing May 15 Recommendations: When produce the summary of your data, don`t forget to store the filter. Introduce the FI routine in your schedule, at the end of the day. AEMET, Agencia Estatal de Meteorología 27